The long-term goals of this project concern a better understanding of the factors controlling the structure and function of the glomerular extracellular matrix. This is a highly specialized structure which is responsible for the maintenance of the glomerular filtration function. Diseases of the glomerulus are frequently associated with alterations in the structural integrity of the glomerular matrix or with the accumulation of abnormal quantities of this material. Glomerular mesangial cells have been found to secrete into culture medium an enzyme activity which can degrade a critical basement membrane component, type IV collagen. This enzyme activity was purified and characterized and found to be a type IV collagenase/gelatinase. Extensive structural analyses suggest that this enzyme may be unique and preliminary experiments using specific antibodies have localized this enzyme to the glomerular mesangium or normal and nephritianimals. It is proposed to continue the structural characterization of this enzyme by molecular cloning and sequence analysis and to determine the degree of expression of this enzyme in several models of nephritis. These expression studies will be performed at the immunohistochemical and in situ hybridization levels, using a new method developed in our laboratory. Finally, the polymerase chain reaction will be used to amplify sequences for related metalloproteases from the glomeruli of normal and nephritic animals, thereby considerably extending our current understanding of the types and patterns of proteolytic enzymes expressed by the intrinsic glomerular cells. This type of information could possibly lead to the development of highly specific inhibitors which could be used to block excessive activity of these enzymes in inflammatory states.